Energy saving pilot valves
April 2013
Pneumatics & Hydraulics
The Series W60 EnergySaver valve is a 5 port, 2 position, sub-base mounted pneumatic valve that supplies full line pressure to port 4 and reduced pressure (2 bar) to port 2. This provides full cylinder force to move the load, but returns the cylinder with less pressure thus reducing compressed air consumption by up to 30%. Although reduced, the pressure in port 2 is enough for quick return of the cylinder. The energy saving function is accomplished by action of the spool and works as quickly as a pressure regulator.
How it works
Traditionally, standard valves apply the same pressure for extending and retracting double acting cylinders. However, this new energy saver valve revolutionises the way cylinders are controlled, by reducing the cylinder retract pressure.
When the solenoid is energised, the valve operates as standard. Supply pressure is directed from the inlet port to port 4 extending the cylinder at full pressure and force. Air in the rod end of the cylinder is exhausted via port 3.
Upon de-energising the solenoid, the pilot valve starts to exhaust the pilot signal from the end of the spool. Momentarily, the spool shifts back to a normal deenergised position directing inlet air to flow to the rod end of the cylinder (port 2 of the valve) and exhausting the cap end. The shuttle now has higher pressure on the opposite side causing it to shift. Shifting the shuttle closes the connection from the spool to the pilot exhaust and opens the cavity at the end of the spool to feedback pressure from port 2.
Meanwhile the cylinder has begun to retract.
Because the actuating end of the spool now has high pressure applied, it starts to shift to the right again closing off the inlet port. Closing the inlet prohibits the air supply from maintaining pressure on the rod end of the cylinder and as the cylinder continues to retract, the pressure drops. This pressure drop reduces the amount of force available to keep the spool actuated against the valve return spring. So, the spool starts to shift back thus allowing an influx of pressure to help retract the cylinder. The valve operates as a fixed spring regulator when in the energy-saving mode, maintaining the cylinder return pressure at approximately 2 bar. Retracting and holding the cylinder with only 2 bar pressure consumes much less air than the standard method of using full pressure to shift and retract.
For more information contact Paul Dunn, Harvard Projects, +27 (0)11 472 9813.
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